Metallurgical slags are produced in the refining of various metals. These slags are produced in a molten form and must be cooled before they can be disposed. A variety of techniques have been employed in the past to cool the slag. The following U.S. patents form a representative, though not exhaustive, list of various slag processing techniques: U.S. Pat. Nos. 505,551 to Iles; 2,139,949 to Forsythe et al; 3,171,736 to Debenham; 3,136,079 to Grady; 4,362,504 to Kajikawa et al; 4,050,884 to Jablin; 3,979,108 to Nagasaki et al; and 2,202,706 to Matela.
The current practice of many iron and steel foundries is to introduce the molten slag into a granulation box which has a water flow of sufficient volume and turbulence at the point of slag impingement to cool and granulate the slag. The water flow then carries the granulated slag away in a trough for dewatering or other processing that may be desired. Generally, the granulated slag is then collected and transported by truck to a landfill or used as ballast in road building, as concrete aggregate, or in the making of glass fibers and so forth.
Unfortunately, the aforementioned technique, as well as other processes where the slag directly contacts the water, has one or more of the following problems. The chunks of cooled slag produced by these processes are relatively large and characterized by a low density mass thereby contributing to high trucking costs. The low density of the granulated slag also may lead to premature landfill aging and may limit the use of the slag in applications where more dense, smaller and less abrasive slag particles are desirable. The granulated slag also tends to cause excessive wear on the pumps and pipes used to transport the mixture for dewatering. Separating the water from the granulated slag is a relatively difficult process. Using conventional techniques where the slag is skimmed from the dewatering tank there still remains a considerable amount of water in the slag which is susceptible to freezing and other problems in cold weather. Settling ponds used in such systems must be dredged periodically to remove the settled solids and the amount of water usage necessary for employing this approach is very high. Moreover, since the cooling and transfer water directly contacts the slag, the water must be treated before it can be safely discharged from the plant.
Those persons knowledgable in the art are undoubtedly aware of other problems that are created by conventionally used slag processing systems.